Find the wrong number in the series: 1, 4, 16, 25, 36

Concept: In this type of number series, each term is the square of a consecutive natural number — 12, 22, 32, 42, 52, 62, … — giving the sequence 1, 4, 9, 16, 25, 36, …

Application:

1. 12 = 1 — matches the pattern.

2. 22 = 4 — matches the pattern.

3. 32 = 9 is expected here, but the series shows 16 (= 42) instead — the pattern breaks at this position.

4. 52 = 25 — matches the pattern again.

5. 62 = 36 — matches the pattern.

Cross-check: lining the given series up against the full reference run of consecutive squares 1, 4, 9, 16, 25, 36 confirms this — the first two terms (1, 4) match the reference exactly, and the last two given terms (25, 36) also match the reference's 5th and 6th squares exactly. Only the reference's 3rd square, 9, is missing from the given series, and the reference's 4th square, 16, has been pulled forward into its place — that jump is what breaks the pattern; the correct value at that position is 9, not 16.

Answer: 16 is the wrong number in the series; it should be 9.